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Method and apparatus for controlling the total overhead used to transmit channel state information in a wireless network

a wireless network and wireless network technology, applied in the field of channel state information, can solve the problem of less uplink channel resources available for transmission of user data on the uplink

Active Publication Date: 2011-03-31
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

For a network using FDMA (Frequency Division Multiple Access) scheduling on the downlink, each mobile station is transmitted to on a subset of downlink subcarriers. The network instructs each mobile station to report channel state information in the uplink only on the subcarriers allocated to that mobile station. This way, each mobile station reports channel state information on a subset of the total available subcarriers, not all of the subcarriers. The network can dynamically modify, preferably in a relatively slow manner, the subset allocated to one or more of the mobile stations as the number of mobile stations reporting channel state information in the cell changes. That is, the number of subcarriers included in the subset assigned to a particular mobile station can be decreased as the number of mobile stations reporting channel state information in the cell increases such that the total overhead allocated for transmitting the channel state information on all of the subcarriers remains generally constant regardless of the number of mobile stations reporting channel state information in the cell.

Problems solved by technology

For a large number of users, the increased feedback load associated with reporting channel state information results in less uplink channel resources being available for transmission of user data on the uplink.

Method used

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  • Method and apparatus for controlling the total overhead used to transmit channel state information in a wireless network
  • Method and apparatus for controlling the total overhead used to transmit channel state information in a wireless network
  • Method and apparatus for controlling the total overhead used to transmit channel state information in a wireless network

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Embodiment Construction

FIG. 1 illustrates an embodiment of a CoMP transmission network 100 where M base stations 110 transmit in the downlink direction to N mobile stations 120. The base stations 110 coordinate with one another to form a super-cell 130, also referred to herein as a CoMP cell. As the number of mobile stations 120 serviced in the CoMP cell 130 increases, the total channel resources are divided up among the various mobile stations 120, e.g. using FDMA scheduling in an OFDM system. The network 100 includes a CoMP processor 140 which can restrict the FDMA scheduler to allocate a known subset S(i) of subcarriers to each mobile station “i”. Each mobile station 1″ is instructed to report channel state information on only the subcarriers included in the allocated subset S(i). The channel state information is reported over an uplink channel. The network 100 can choose to transmit to mobile station 1″ on only a fraction of the subcarriers included in S(i), this fraction of downlink transmission subc...

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Abstract

An amount of total overhead allocated by a wireless system for transmitting channel state information by a plurality of mobile stations serviced by the wireless system can be controlled by allocating a reporting interval, reporting size and subset of subcarriers to each of the mobile stations for use by the mobile stations in reporting channel state information on the subcarriers included in the subset allocated to the respective mobile stations. At least one of the reporting interval, reporting size and subset of subcarriers allocated to one or more of the mobile stations is modified as a function of the number of mobile stations reporting channel state information so that the total overhead allocated for transmitting the channel state information on all of the subcarriers remains generally constant regardless of the number of mobile stations reporting channel state information.

Description

TECHNICAL FIELDThe present invention generally relates to channel state information, and more particularly relates to controlling the amount of overhead used for the feedback of channel state information in a wireless network.BACKGROUNDCoherent CoMP (Coordinated Multi-Point) transmission on the downlink significantly improves spectral efficiency and cell-edge bitrate of cellular systems. Coherent CoMP requires the network to know the state of the downlink channels allocated to each mobile station from a number of network antennas that are received strongly by each mobile station. In FDD (Frequency-Division Duplexing), the channel state information (CSI) is transmitted from each mobile station to the network on the assigned uplink channel. For an OFDM (Orthogonal Frequency-Division Multiplexing) system with FDD, let W denote the total number of subcarriers in the system, N the number of users reporting CSI per cell, B the average number of bits required to report the channel state in...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04W72/04
CPCH04B7/0658H04L1/0026H04L5/0058H04L5/0053H04L1/003
Inventor ZANGI, KAMBIZ
Owner TELEFON AB LM ERICSSON (PUBL)
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